NSE4 High Availability and Diagnostics Practice Question
A network engineer is configuring an SD-WAN rule to steer voice traffic to the MPLS link with the lowest latency. The SLA target is set to latency < 50 ms and jitter < 10 ms. However, the MPLS link occasionally exceeds the latency threshold. What should the engineer do to ensure voice traffic uses the best available link without manual intervention?
⚠ Common exam trap
Many exam-takers think increasing SLA thresholds or disabling SLA enforcement solves the problem, but the correct approach is to implement a fallback strategy to maintain SLA compliance automatically.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the SD-WAN rule with a secondary strategy to use the broadband link when SLA is not met.
Configuring a secondary strategy (e.g., fallback to broadband) allows the SD-WAN rule to automatically steer voice traffic to the best available link when the primary MPLS link fails the SLA (latency > 50 ms). This ensures continuous SLA compliance without manual intervention, leveraging Fortinet's SD-WAN dynamic path selection based on real-time performance metrics.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Remove the latency performance SLA and rely only on jitter.
Why it's wrong here
Removing latency from the performance SLA leaves jitter as the only measured metric, so the SD-WAN health check will no longer flag the MPLS link when latency climbs. Since voice QoS is degraded by high one-way delay, the rule would keep sending traffic along the high-latency MPLS path and failover never triggers. That defeats the purpose of steering voice traffic away from an underperforming link.
- ✓
Configure the SD-WAN rule with a secondary strategy to use the broadband link when SLA is not met.
Why this is correct
A correct fix is to set the SD-WAN rule to use the broadband link as a secondary strategy when the primary MPLS link fails its performance SLA. In Fortinet, this is done by listing multiple link members in the rule and specifying a strategy such as 'best quality' or 'SLA' where the next available member is used as a backup. The rule then automatically moves voice traffic to broadband whenever the MPLS link violates the configured latency threshold.
- ✗
Increase the jitter threshold to 15 ms to avoid SLA violations.
Why it's wrong here
Raising the jitter threshold to 15 ms only makes the SLA more tolerant to jitter; it has no effect on the latency measurement that is causing the MPLS link to be down. If the latency metric is already part of the SLA, reducing the bar for a different metric won't prevent the violation. It could even mask genuine jitter problems, making voice quality worse while still failing over for latency only when latency itself reaches the threshold.
- ✗
Disable SLA enforcement on the SD-WAN rule so voice traffic always uses the MPLS link.
Why it's wrong here
Disabling SLA enforcement removes the link health check from the SD-WAN rule, so FortiGate will not evaluate MPLS latency and will never move traffic to the broadband link. The rule would unconditionally pin voice traffic to MPLS, including when latency is high, because there is no failure condition to trigger the secondary strategy. This is the opposite of what is needed for latency-sensitive VoIP.
Go deeper
Related to this question
About these practice questions
This NSE4 question is part of Courseiva's 773-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE4 practice question is part of Courseiva's free Fortinet certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the NSE4 exam.